It has long been recognized that, in connection with the pneumatic or gas conveying of plastic particles, i.e. polyethylene, polypropelene, etc., that conduit interior wall treatment is desirable for the purpose of minimizing the formation of fines and streamers during the particle conveying operation.
Representative of prior art efforts in this connection are the following United States Patents:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 2,784,038 G. Schneider March 5, 1957 2,834,059 H. H. Hoelzel May 13, 1958 3,117,821 L. E. Mylting January 14, 1965 3,380,783 J. C. Hunter April 30, 1968 3,464,740 S. R. Scruby et al September 2, 1969 3,719,207 H. Takeda March 6, 1973 3,912,474 W. H. H. Drews October 14, 1975 ______________________________________
It has also been recognized, heretofore, that stainless steel conduits may be shot-peened, utilizing a Hodge Clemco Ltd. "Holloblast" nozzle for the purpose of producing a roughened surface, having a "dappled" finish, for the purpose of minimizing the formation of "smears" when particle nibs come into contact with the conduit wall during the conveying operation.
However, so far as is presently known, it has not heretofore been disclosed in the prior art that fines and streamers can be minimized and/or prevented to a substantial degree, or to a significantly improved extent, by maintaining a particular relationship between the longitudinal flow direction of particles through shot-peened conduit means and the original impact angle of the shot employed during the fabrication of such shot-peened conduit means.
Specifically, this invention contemplates methods as subsequently described, along with conduit apparatus resulting from the implementation of such methods.
The basic method aspect of the invention is characterized as follows.
This basic method for reducing the formation of fines and streamers in the gas conveying of plastic particles, is applicable where
the interior of a plurality of particle conveying conduit sections are treated by PA0 assembling the plurality of shot-peened, particle conveying conduit sections to define conduit means wherein the apexes of the acute, impacting angles all point generally in an intended longitudinal flow direction of the plastic particles; and PA0 flowing the plastic particles through said assembly of shot-peened particle conveying conduit sections in the intended flow direction with
shot-peening the interior wall means of each of these sections, with shot being impacted against the wall means of each of the sections at an acute, impacting angle, the apex of which points generally longitudinally of each said section toward one end thereof. PA1 the generally longitudinal flow direction of the particles through each section forming, at the shot-peened interior wall means thereof, an acute, particle flow to shot impact direction related angle, with respect to the directions of impacting of the shot, with these angles being oriented in each of the sections with the angle apex thereof generally pointing toward the afore-said one end thereof.
The improvement afforded by the method resides in the steps of:
Further aspects of the invention reside in the arrangement wherein the acute, particle flow to shot impact related angle comprises about 30 to 45 angular degrees and resides in the arrangement wherein the particle conveying conduit sections are fabricated of aluminum and the shot which was used in shot-peening comprises chilled steel shot.
Having described the general background and nature of the invention, it is now appropriate to give consideration to a preferred format for practicing the invention. This format will be described with reference to exemplary drawings which accompany this application.